We computed Higuchi's fractal dimension (FD) of resting, eyes closed EEG recorded from 30 scalp locations in 18 male neuroleptic-naïve, recent-onset schizophrenia (NRS) subjects and 15 male healthy control (HC) subjects, who were group-matched for age. Schizophrenia patients showed a diffuse reduction of FD except in the bilateral temporal and occipital regions, with the reduction being most prominent bifrontally. The positive symptom (PS) schizophrenia subjects showed FD values similar to or even higher than HC in the bilateral temporo-occipital regions, along with a co-existent bifrontal FD reduction as noted in the overall sample of NRS. In contrast, this increase in FD values in the bilateral temporo-occipital region was absent in the negative symptom (NS) subgroup. The regional differences in complexity suggested by these findings may reflect the aberrant brain dynamics underlying the pathophysiology of schizophrenia and its symptom dimensions. Higuchi's method of measuring FD directly in the time domain provides an alternative for the more computationally intensive nonlinear methods of estimating EEG complexity.

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Introduction: Apolipoprotein E4 (ApoE ε4) polymorphism is a known genetic risk factor for Alzheimer’s disease (AD). Objectives: To evaluate the role of ApoE ε4 on white matter structural integrity in AD. Methods: Subjects were 32 patients with probable AD (ApoE ε4-positive: n = 15) and 18 matched controls (ApoE ε4-positive: n = 6). All subjects were right-handed, evaluated using standard scales and genotyped at the ApoE locus. Diffusion tensor imaging was performed with a 3-tesla MRI scanner and analyzed using the tract-based spatial statistics method. Results: AD patients had significantly lower fractional anisotropy (FA) in bilateral temporoparietal, limbic and parahippocampal regions in comparison to healthy comparison subjects. ApoE ε4 carriers among both AD and healthy comparison subjects showed lower FA in limbic and medial temporal regions. Conclusions: There is a modest association between ApoE ε4 carrier status and reduction in white matter tract integrity at medial temporal and limbic regions in both healthy and AD subjects.

Activation of the bilateral dorsal anterior insula, a component of the central salience network, was found to be unique to this 'endogenous-cue prospective memory task' in comparison to previously reported exogenous- and endogenous-cue prospective memory tasks without incremental working memory updating. Thus, the findings of the present study highlight the important role played by the dorsal anterior insula in incremental working memory updating that is integral to our endogenous-cue prospective memory task.